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Bi-monthly meeting of MIT-BNL He3-ABS Collaboration
Meeting Minutes – Sep 25, 2025 (10:00 AM)
Attendees
- Prajwal MohanMurthy
- Medani (he/him)
- Haixin Huang
- Richard G. Milner
- Jim Kelsey
- (Mention of Frank, and others indirectly)
1. Presentation: Heat Deposition & Storage Cell Geometry
- Presenter: Medani summarized results (building on his July 31st presentation).
- Geometry details: Based on HSR polarimeter and helium-3 storage cell (approx. 60 cm long, 1 cm diameter).
- Constraints: Must match pC polarimeter dimensions (12.4 cm end dimensions).
- Discussion:
- Initial inner diameter (10 mm) may be too small for AGS beam → proposal to increase to 15 mm.
- Tapering lengths (~200 mm) motivated by space constraints (~1 m available excluding pumps).
2. Simulation Results
- Method: CST simulations using worst-case proton beam parameters.
- Findings:
- At room temperature, total resistive wall heating ~4.6 W (3.95 W in the narrow tube, 0.62 W in cones).
- Increasing diameter (10 → 20 mm) reduces wakefields and losses by > factor of 2.
- At cryogenic conductivity (10 K aluminum), losses reduced further by factor ~6 compared to 300 K.
- Analytical formula matches CST results, confirming reliability.
3. Clarifications & Discussion
- Bunch charge: Debate on whether 30.5 nC or 64 nC is correct. Needs follow-up (Prajwal to share TDR screenshot).
- Cooling capacity: Cryostats can handle ~10 W. Even in worst cases (with doubled bunch charge), heating remains manageable (<10 W).
- Conductivity values:
- NIST vs. CRC databases give different extrapolations at low T.
- NIST data flattens below ~10–20 K; CRC predicts exponential rise.
- Conclusion: NIST values are trusted.
- Higher conductivity is beneficial due to skin-depth effects (lower eddy current heating).
- Materials: Pure aluminum remains suitable; no need to switch to stainless steel.
4. Engineering Considerations
- Practical build: Cooling connection via cryogenic storage chamber modeled on Hermes design (Jim Kelsey noted engineering challenges: thin-wall cells, thermal isolation, beryllium fingers, wakefield suppressors).
- Progress update (Prajwal):
- Cryo stand and 14-inch cryo insert ready.
- Insert remounted successfully with existing stand (with minor adjustments).
- Copper tubing wrapped around pots; undergoing oxide removal, nickel coating, this week and vacuum brazing next week.
5. Comments & Endorsements
- Richard G. Milner: Confirmed results are reasonable, consistent with prior experience with ultra-pure aluminum cryogenic cells.
- Jim Kelsey: Raised engineering integration points; confirmed challenges are solvable.
- Consensus: Calculations and simulations support feasibility; heat deposition is within acceptable limits.
6. Action Items
1. Prajwal – Share TDR screenshot on bunch charge (30.5 vs. 64 nC).
2. Prajwal – Draft a two-page summary document with simulation guidance.
3. Team – Continue with cryo insert assembly and brazing process.
Meeting adjourned after technical updates and clarifications.